Venetian blind



Nov. 24, 1964 lsAMU. u uu KA 3,158,196

United States Patent O 3,158,196 VENETIAN BLIND Isamu Fukuoka, 993 Zaimokuza, Kamakuro-shi,

Kanagawa-ken, Japan Filed June 24, 1963, Ser. No. 290,925 Claims priority, application Japan, June 25, 1962,

33,242 3 Claims. (Cl. 160-173) The present invention relates to a slat lifting mechanism tor a Venetian blind of the type wherein a plurality of blind slats are suspended from a head box in the shape of a ladder by means of suspender tapes and raised or lowered by means of litter tapes.

The conventional Venetian blind of this type employs two or more litter tapes, each ot which is passed through the vertically aligned openings in the blind slats and is fixed at the upper end thereof onto a litter drum mounted on a litter shaft in the head box and at the lower end thereof to a bottom plate. The blind slats can be raised by rotating the litter shaft in one direction so as to wind up the litter tapes onto the respective litter drums to raise the bottom plate, and the slats can be lowered by rotating the litter shaft in the other direction so as to unwind the litter tapes from the respective litter drums to lower the bottom plate.

In such a conventional Venetian blind, the rotation of the litter shaft in the slat lowering operation must be stopped just when the slats have been fully lowered, that is, the litter tapes have been completely unwound from the litter drums, and if the rotation is inadvertently continued after the tapes have been fully unwound the tapes will be wound up onto the litter drums in the direction opposite to the normal winding up direction, which may damage or break the litter tapes.

Also, the rotation of the litter shaft in the slat lower ing operation must be stopped if the bottom plate comes into contact with some obstacle which prevents the bottom plate from further lowering. The continued rotation of the lifter shaft will unwind the lifter tapes notwithstanding the slats being not able to move downward, thus resulting in the damages of the litter tapes and/blind slats.

It is an object of the present invention to avoid the above-mentioned difiiculties in the conventional slat lifting mechanism for the Venetian blind.

In accordance with the present invention the slat lifting mechanism for the Venetian blind is provided wherein the litter tape is not directly fixed to the litter drum but is connected thereto through the intermediary of friction means which is in tight frictional engagement with the litter drum so long as the weight of the bottom plate is imposed on the litter tape but in loose frictional engagement when the weight of the bottom plate is not imposed. The friction means may be made of a spring having a drum engaging portion or portions encircling the litter drum and a tape fixing portion to which the upper end of the lifter tape is fixedly connected.

In order that the invention will be more fully understood and readily `carried into effect, the following detailed description is given with reference to the accompanying drawings in which:

FIGURE 1 is a front elevation of a slat lifting mechahead box (not shown) as in'the conventional construction of the Venetian blind; Usually two or more litter drums 2 are mounted on the litter shaft 4 to raise the bottom plate at two or more spaced points of the slats. r

A spring 5, which is shown clearly in FIGURE 2, encircles the groove 1 of the litter drum 2. The spring as shown in the drawings has two helically wound portions at the both ends thereof, Which are not fixed but wound around the groove 1 in the direction corresponding to that of the slat raising rotation of the litter shaft, and a tape fixing portion 3 at its central part to which the upper end ot a litter tape 6 is fixed. Alternatively the spring may have only one helically .wound portion at one end and the tape fixing portion at the other end.

Normally the weight of the bottom plate (not shown) applied to the lower end of the litter tape 6 acts to tighten the helically wound portion of the spring 5 into tight frictional engagement with the peripheral surface of the tape winding groove 1 of the litter drum.

When the litter shaft 4 is rotated in the slat raising direction, the spring 5 is more firmly tightened on the periphery of the groove 1 since the spring 5 is wound around the groove 1 in the direction corresponding to that of the slat raising rotation of the litter shaft 4, so that the spring is rotated with the litter drum and -thus the litter tape 6 is wound up onto the drum to raised the blind slats.

When the litter shaft 4 is rotated in the opposite direction, namely, slat lowering direction, the spring 5 is rotated with the litter drum and the litter tape 6 is unwound from the drum to lower the blind slats. Thus. the raising or lowering of the blind slats can be accomplished by the rotation of the litter shaft 4 in one or other direction.

When the slat is completely lowered, that is, the bottom plate reaches to the lowest position, the weight of the bottom plate becomes supported entirely by suspender tapes (not shown) and the weight load is relieved from the lower end ot the litter tape. The spring is loosened into loose fiictional engagement with the peripheral surface of the groove 1, so that the rotation of the drum is not transmitted to the spring, Which is held stationary even if the rotation of the litter shaft is continued.

Also, if the bottom plate comes into contact with some obstacle on the way of the lowering path, the load is relieved from the lower end ot the litter tape, so that the rotation of the litter drum is no longer transmitted to the litter tape. v

It will be understood from the above explanation that in accordance with -the present invention the unwinding of the litter tape is automatically stopped When the slats are fully lowered or when the bottom plate comes into r contact with some obstacle which prevents it from further lowering, even if the rotation of the litter shaft is continued.

Although a specific embodiment of the present invention has been described, it should not be construed as limited thereby but to include various other equivalent features as set forth in the claims appended hereto.

It is understood that any suitable changes, modifications and variations may be made without departing from the spirit of the invention.

What is claimed is:

1. In a slat lifting mechanism for a Venetian blind, the improvement comprising a litter shaft, a litter drum mounted on said shaft, a blind slat lifting tape adapted to be wound up onto the litter drum, and frictional means which is fixed to the upper end of the litter tape and frictionally engages with the litter drum by a load applied to the litter tape.

2. In a slat lifting mechanism for a Venetian blind, the

Patented' Nov. 24, 1964 improvement comprising a lifter shaft, a lifter drum mounted on said shaft, a blind slat lifting tape adapted to be wound up onto the lifter drum, and spring means fixedly connected to the upper end of said tape and having a portion frictionally engaging the litter drum.

3. In a slat lifting mechanism for a Venetian blind, the improvement comprising a lifter shaft, a lifter drum mounted on said shaft, a blind slat lifting tape adapted to be wound up onto the litter drum, and a spring having a portion fixedly connected to the upper end of said lifting tape and at least one helical portion Wound around said lifter drum.

References Cited by the Examiner UNITED STATES PATENTS Alderson et al. 254-187 Litchfield 192 41 Ragsdale.

Sheard 254-186 X Clausing et al 192-41 Sacchini et al.

10 HARRISON R. MOSELEY, Primary Examiner.

REINALDO P. MACHADO, Examiner. 

1. IN A SLAT LIFTING MECHANISM FOR A VENETIAN BLIND, THE IMPROVEMENT COMPRISING A LIFTER SHAFT, A LIFTER DRUM MOUNTED ON SAID SHAFT, A BLIND SLAT LIFTING TAPE ADAPTED TO BE WOUND UP ONTO THE LIFTER DRUM, AND FRICTIONAL MEANS WHICH IS FIXED TO THE UPPER END OF THE LIFTER TAPE AND FRICTIONALLY ENGAGES WITH THE LIFTER DRUM BY A LOAD APPLIED TO THE LIFTER TAPE. 